Motor control for electric hoists



1945- c. J. MANNEY EIAL 2,386,487

MOTOR CONTROL FOR ELECTRIC HQISTS Z SheetS-Sheet l Filed Oct. 3, 1942 d- 1945- c. J. MANNEY EFAL 8 MOTOR CONTROL F OR ELECTRIC HOISTS Filed Oct. 3, 1942 2 Sheets-Sheet 2 Patented Oct. 9, 1945 2,386,487 MOTOR CONTROL FOR ELECTRIC HOISTS Charles J. Manney, Kenmore, and Harry D.

Moore, Buffalo,

N. Y., assignors to Columbus McKinnon Chain Corporation,

Tonawanda,

N. Y., a corporation of New York Application October 3, 1942, Serial No. 460,650

3 Claims.

It is well known to those skilled in the art that it is common to place temperature-responsive means in the supply circuit of an electric motor so that when an abnormal overload on the motor occurs, the heat-responsive means will interrupt the current to the motor, and keep the circuit open until such time as the motor has had sufiicient time to cool.

Furthermore, it is well known that such an arrangement of controls has been contemplated in connection with electrically driven hoists. When, however, the current to the motor of the hoist is interrupted by reason of an overload, the hoist is thereby made inoperable and the load suspended therefrom must be allowed to remain in mid-air during and up to such time as the motor has had opportunity to cool off sufiiciently to allow the closing of the temperature-responsive means and again permit the passage of current through the windings of the motor. Such a condition is not only annoying and places the hoist temporarily out of service, but is hazardous to the safety of those around the hoist. Moreover, the load must be sustained by the hoist unnecessarily long with possible resulting strain and when the hoist is handling material. where time is an element, such as molten metal, for instance, the delay involved might result in great loss.

We have sought to overcome this drawback in the use of temperature-responsive means as applied to the electric motor of an electrically driven hoist; and, the principal object of our invention has been, therefore, to combine such temperature-responsive means with the hoisting circuit only of the motor so that when an overload occurs, the hoisting circuit only will be opened, thus leaving th lowering circuit uninterrupted so that it may be actuated to lower the load to a suitable resting place.

The above objects and advantages have been accomplished by the device shown in the accompanying drawings, of which:

Fig. 1 is an elevational view showing in outline the control end of an electric hoist to which our invention has been applied, also showing in diagrammatic manner, the electric circuit thereof;

Fig. 2 is a similar view of a modified form of temperature-responsive means;

Fig. 3 is a wiring diagram of our invention applied to a three phase circuit similar to that of Fig. 1 but connected directly to the power line;

Fig. 4 is a wiring diagram showing the form of invention of Fig. 2 as applied to a single phase or two-wire circuit.

For clearness of illustration, all the parts of our device are diagrammatically represented, no mechanical parts bein shown except the outline of the hoist casing and this is because the switches and push button unit are standard articles of manufacture, and therefore only the contacts thereof are shown in the drawings.

Referring to the form of invention shown in Fig. 1, a contactor i0 is diagrammatically illustrated. This contactor is a standard article of manufacture and is the kind equipped with contacts for causing the motor connected therewith to be elevated or lowered. In the form of hoist to which our invention is applicable, it is preferable to use a transformer for the push button circuit and such a transformer is represented at H. The parts, together with the electric motor, are encased within the hoist housing which is represented at 12. The push button for operating the hoist is represented at l3.

The forms of invention shown in Figs. 1, 2 and 3 and the circuit diagrams thereof are as applied to hoists operated by three-phase current and, therefore, three power lines l4, l5 and I6 are shown.

The contactor I0 is provided with a group of hoisting contacts -2il2l, 2223, 24-25 and with a group of lowering contacts 35-3l, 3233, and 3435. Contacts 2! and 30, 23 and 32, 25 and 34 are connected together by means of jumpers 36, ll and 42, respectively.

The hoisting group of contacts is provided with a movable member .43 which carries contact arms .44, 45 and it for engagement respectively with contacts 20--2,i, 2223, and 24-25. In like manner the lowering group of contacts is provided with a movable member having contact arms 51, 52 and 53, which engage respectively contact members 36-3l, 3233, and 34-35.

The contacts just above described are stationary and the arms of each group are moved by and with the movable members to close either group of contacts. Also carried by the movable member 43 is a contact arm 54 which normally connects two stationary contacts 55 and 56. Similarly a contact arm carried by the movable member 50 serves to normally connect stationary contacts 6i and 62. The movable member 43 actuating the hoisting group of contacts is operable by means of a solenoid 63, and in like manner, the movable member 50 of the lowering group of contacts is provided with an operating solenoid 6 3. The normally closed contacts 55 and 56 of the hoisting group are connected in series with the solenoid 64 of the lowering group, and

connected by means of a lead the contacts BI and 62 of the lowering group are connected in series with the solenoid 63 of the hoisting group. By this arrangement, the solenoid of the lowering group is interlocked and prevented from being operated while the hoisting group is energized by the opening of the contacts 55 and 55 of the hoisting group. Likewise the hoisting group is interlocked while the lowering group is energized by the interruption of the current through the solenoid 53 by the opening of contacts GI and 62.

In the form of invention shown in Fig. 1 we employ two overload relays I and I I. These relays are of the type in which a temperatureresponsive switch is provided and which is controlled by a heating coil through which the current to the motor passes. The heating coils of these relays are represented at I2 andI3, respectively, and the switches thereof at I4 and I5, respectively. When these relay coils are heated to a predetermined temperature they cause ,the switches to be opened and thus interrupt the current flowing therethrough.

The pushbutton I3 is a stardard article of manufacture having a switch arm 80 for closing the hoisting contacts 8| and 82 of the switch, and a switch arm 83 for closing the lowering contacts '84 and 85.

The transformer I I shown in the drawings has, as is customary, a primary coil 90 and a secondary coil 9|. One side of the primary coil is 92 to the power line M- through jumper 42, the other side of this winding being connected by means of lead 93, jumper GI 'and lead 95 to one side of the coil I2 of the relay Ill. The other side of this relay coil is connected by means of lead 95 to the power line I5. One side of the coil I3 011 relay II is connected by means of a lead 96 to the power line I6. The other side of this relay coil is connected by means of lead IM to jumper 4G and thereby to contacts 2| and 30.

The secondary winding M of the transformer to the common terminal point is connected at one side by means of lead IUI to I the push button unit I3 and has a common connection to hoisting contact 82 and the lowering contact 85 thereof, thus energizing these two contacts of the unit. When the hoisting contact arm 8!! is depressed current is conducted from live contact 82 to contact BI and thence over lead I02 to thenormally closed contact 62 of the lowerin'g group and through contact arm BI] and contact 5| thereof to the solenoid 63 of the hoistin group thereby actuating the movable member 43 ofthis group and causing the normally open contacts 20-2I, 22-23 and 24-25 thereof to be closed, at the same time opening the normally closed contacts and 56 and thus locking the solenoid 54 of the lowering group against being energized. With contacts 2II2I, 22-23, and 24-25 closed, current will flow to the motor II from contact 20 over lead I03 to terminal I06 of the motor, and current will also flow from contact 22 over lead I85 to terminal I04 of the motor, and current will also flow from contact 24 over, lead IBI to terminal I58 of the motor, thereby causing the motor to rotate in the direction which will effect hoisting of the load. It will be obvious that the current flowing to the motor from contacts 20 and 22 willpass through the coils I3 and 12, respectively, of the relays II and III. As hereinbefore stated, these relays are so constructed that in the event of excessive overload on the motor of the hoist the heat produced by the coils I2 and I3 will cause the switches I4 and 15, respectively, to be opened. As shown in the drawings both of these relay switches are connected in series and one of the contacts of the switch I5 is connected by means of lead I89 to one side of the solenoid 53 of the hoisting group of contacts. One of the contacts of the switch I I is connected by means of a lead I II] to common terminal point I I I which is in turn connected to one side of the secondary winding 9| of the transformer by means of lead I I2. Since the switches of the relays are connected in series with each other and with the solenoid 53 of the hoisting group of contacts it is obvious that they will be actuated by the heat produced in the coils I2 and I3 by reason of overload, the current to the solenoid of the hoisting group of contacts will be interrupted, and thereby permit the movable element t3 thereof to return all live contacts to their open positions, thus interrupting the current to the motor and preventing further hoisting of the load. When these switches are thus'opened by excessive'heat in the coils of the relays, the load cannot be elevated further until the motor and coils have cooled sufi'iciently to permit the switches I l and I5. to assume again their closed positions.

Even though the hoisting current is interrupted and locked out by relays III and I I, the reverse or lowering current is not disconnected so that our hoist may be operated in a downward direction, thus permitting the lowering of the load to a safe place. When the hoist is to be lowered, the movable element 83 of the push button I3 is actuated to connect contacts and 84 whereby current will flow from the live contact 85 through the arm 83 to contact 84 and thence over lead I I3 to contact 55 and over contact arm 54 to contact 56, thence through the connected solenoid 64 of the lowering group of contacts. From the other side of the solenoid current will flow over lead I I4 I I I returning to the secondary of the transformer over lead H2. The circuit just traced is unaffected by the heated condition of the motor or the coils of the relays and, as just indicated, permits the load to be lowered and disconnected from the hoist if desired.

When the movable member 50 of the lowering group has been actuated by the energization of its solenoid 66', contact arms 5|, 52 and 53 of the movable element will connect contacts 3II--3I, 3233, and 34-35. Current will then flow to the motor from energized contacts III, 33 and 35 over the jumper leads H5, H6, H1, respectively, which connect these live contacts, respectively, with leads I05, I53 and IIILthus carrying current to the terminals I04, I06 and I58, respectively, of the motor. It will be noted that the jumper lead I I5 connects the contact 3| of the lowering group with the contact 22 of the hoisting group. In likev manner the contact 33 of the lowering group is connected to the contact 29 of the hoisting group. By reason: of this cross-over of contacts, when current passes to the motor over the circuits just above described, the direction of rotation of the motor will be reversed.

As hereinbefore pointed out, in the form of invention shown in Fig. 1 we have shown thermal overload relays of the type having a heating coil and a relay switch of such construction that when excessive current is passed through the coils to the motor, caused either by an overload, a ground, or a short-circuit, the switches will be thermally actuated and caused to interrupt the current, thus stopping the motor. Instead of this type of relay, it is obvious that we may use a heat-responsive element either inclosed within the motor or insuch proximity thereto as to be affected by the heat generated within the motor. Such a construction is shown in Fig. 2 where the motor is represented at I20. The temperature-responsive switch I2I is shown diagrammatically as being located within the housing of the motor. In this figure all similar contactors and circuits bear the same numerals as those in the form of invention shown in Fig. 1. In this form of invention the contact SI of the push button I3 is connected to the contact I22 of the switch I2I, by means of the lead I23, the other contact I24 of the switch being connected to the normally closed contact 62 of the contactor Ill by means of a lead I25. From contact 62 the current is conducted to the solenoid 63 of the hoisting group and thence over leads I26 and I33 to one side of the secondary 9| of the transformer II. Current is supplied to the live contacts 82 and 83 of the push button by means of the lead III! which is connected to the opposite side of the secondary of the transformer. The lowering contacts 85 and 84 of the push button are connected through the contact arm 83 to the normally closed contact 55 of the hoisting group by means of lead II3. From contact 55 current will flow over contact arm 54 to contact 55 and thus to the solenoid 54 of the lowering group. From solenoid 64 current is conducted back to the secondary winding 9| of the transformer by means of leads H4 and I33. Leads I03, I65 and H31 extending from the controller ID and from the motor I are for convenience of illustration shown broken ofi but these are connected together in a manner similar to that shown in Fig. 1.

While we have shown in Figs. 1 and 2 the use of a transformer to supply current at a reduced voltage to the circuit through the push button and through the temperature-responsive switches, it is obvious that these protective devices may be connected directly in the power line. Such a construction is shown in Fig. 3. This circuit is very similar to that of Fig. 1 substantially the only difference being that the live contacts 82 and of the push button receive their current directly from the power line I4 through contact 25 and over lead I3I. Furthermore, currentwill flow from the hoisting contact SI, over lead I32, contacts 32 and BI, through contact arm 63, solenoid 63, lead I33 and through switches 15 and T4 to contact 23 over lead I74, and thence to power line I5. The other parts of the circuit are substantially like those of Fig. l and will not again be described. As stated in connection with the form of Fig. 2, the motor leads I33, I95 and I9! are connected to the motor as illustrated in Fig. 1.

Our invention is applicable not only to threephase current as hereinbefore described but also to single-phase alternating current or to direct current. Such an arrangement is shown in the form of invention illustrated in Fig. 4. In this form current is conducted to the contactor I32 over leads I33 and I34. The contactor I32 for this kind of current is provided with normally open groups of contacts Mil-MI, I42--I43 and I'I5-I'I6 in the hoisting group and normally open groups of contacts I44I45, I43 I4'I and I 'I'II'I8 in the lowering group. The hoisting group has normally closed contacts I5lJ-I5I, and the lowering group has contacts I52--I53. As shown in this figure no transformer is used and current from the feed lines is used to actuate the push button circuit. The live contacts 82 and 8'5 of the push button unit I3 are, therefore, energized over lead I54 which receives current from power line I34 preferably through contact I43. When the push button is actuated by the depression of the arm to cause the hoist to be elevated, current will flow to contact 8| of the push button and over lead I55 to one terminal of the temperature-responsive switch I56. From the other side of this switch current will flow through lead I50 to the solenoid IBI of the hoisting group of contacts of the contactor. Thence current will be conducted to normally closed contacts I52-I53 and over lead I52 to the other power line I33 through contact I4I. When the solenoid IfiI is energized the movable element IE! will be actuated and current will flow from the energized contacts I 45 and i i-2 over leads I53 and I 63, respectively, to the reversing terminals IIQ-I I33. When the push button controlling the lowering arm 83 is actuated current will flow from live contact to contact 84 of the switch and thence over lead I33 to the normally closed contacts I Eli-J El and through solenoid I8! of the lowering group thus causing its movable element I10 to be actuated and thereby closing normally open contacts I'M-445 and I4i3-I4'I. Current will flow from the other side of the solenoid I57 to contact IL I and lead I33 over lead I52. Due to the fact that contacts I41 and I45 of the lowering group are connected, respectively, to contacts M9 and E42 of the hoisting group by means of jumper leads Ill and H2, respectively, the current supplied to the motor over leads E63 and ital will be reversed. However, since a single-phase alternating current motor or a direct current motor can be reversed only by reversing one of its windings, the motor IE5 is shown with two additional, non-reversing terminals I 8I and IE2. These terminals are connected, respectively, to contacts I46 and H5 of the controller I32 by means of leads I85 and I83, respectively. A jumper lead I33 connects the contacts lit and H7, and a jumper lead I84 connects the contacts I74 and I18, whereby cur rent received by the motor from contact I15 when hoisting or from contact Il'8 when lowering will not be reversed, but due to the reversal of the current supplied to terminals I19 and I80, as hereinbefore described, the motor will be operated in a lowering direction.

While we have shown the application of our invention to single-phase alternating or direct current, utilizing a temperature-responsive device similar to that shown in Fig. 2, which receives its heat from the motor, it is obvious that the type of temperature-responsive relay shown in Fig. 1 may also be used. Obviously only one relay is necessary and when used it will be connected in one of the two power lines I33 or I34 of the two-wire circuit in substantially the same manner as shown in connection with the power lines IG and I5 of the form of invention of Fig. 1.

It will be obvious from the foregoing that there are three distinct circuits in our invention, which might be characterized as a power circuit, a motor circuit, and a control circuit. We have endeavored to show a distinction between these circuits by the width of lines employed in the drawings in illustrating them. The power circuits are shown in the heaviest lines, the motor circuits are shown in the medium width lines and the control circuits are shown in light lines. The power circuits consist of the leads I4, I5 and I6, the coil I2 and 73 of the relays I0 and II, respectively, and the primary of the transformer II in the forms illustrated in Figs. 1 and 2. The

except that the transformer is omitted.

power circuits in the form of Fig. 3 are similar The power circuits of the form of Fig. 4 consist simply of the leads I33 and I34 which are connected, respectively, to the contacts MI and I43. The motor circuits consist of the leads I03, I05 and IE1 together with the jumper leads H5, H6 and II I in Figs. 1, 2 and 3. Similar circuits in the form of Fig. 4 comprise the motor leads I63 and I64 togethe with the jumper leads Ill and H2.

The control circuits comprise the secondary 9 I of the transformer in Figs. 1 and 2, the contacts 8IB2, 84--85 and the contact arms 80 and B3 of the push button I3, solenoids B3 and 64, and the temperature-responsive switches I4 and I5 of the form of Fig. 1. In the form of Fig. 2 the temperature-responsive element of the switch [2i forms a part of the hoisting control circuit. The leads connecting these various parts of the invention are of course included in the control circuits.

The control circuits of the form of Fig. 3 are similar to those of the form of Fig. 1 except that the secondary 9| of the transformer of Fig. 1 is not included. The control circuits of the form of Fig. 4 include the contacts and contact arms of the push button together with the temperature-responsive switch I56 of the motor, the two solenoids IfiI and I61 together with the leads connecting these parts, as hereinbefore described.

While we have shown our invention as applied to a hoist having but one speed, it is obvious that it may be used upon a hoist having a slow speed control circuit and a high speed control circuit. When so used, our invention would be connected so as to control the hoisting circuits at either or both speeds of operation.

Having shown and described our invention, we claim:

1. A hoist having a reversible electric motor, a motor hoisting circuit for operating said motor, a motor lowering circuit for operating said motor, a hoisting control circuit for one of the motor circuits, a lowering control circuit for the other motor circuit, said control circuits being energized separately from and having no part in common with said motor circuits, a separate manuallycontrolled device for causing each of said control circuits to be energized and de-energized, and an emergency thermal cutout device associated with one of the hoisting circuits and actuated only by an emergency temperature rise in the motor during its hoisting operation, said cutout device being operable independently of the motor lowering circuit and its associated lowering control circuit, and being responsive to said emergency temperature to open the associated hoisting circuit prior to stalling the motor, said lowering circuits being unafiected by the interruption of the hoisting circuits.

2. A hoist having a reversible electric motor, a motor circuit for operating said motor to hoist a load, a motor circuit to operate said motor to lower a load, a hoisting control circuit .for one of the motor circuits, a lowering control circuit for the other motor circuit, said control circuits being energized separately from and having no part in common with said motor circuits, a separate manually-controlled device for causing each of said control circuits to be energized and deenergized, and an emergency thermal cutout device associated with the hoisting control circuit and actuated only by an emergency temperature rise in the motor during its hoisting operation, said cutout device being operable independently of the lowering control circuit and being responsive to said emergency temperature to open the hoisting control circuit prior to stalling the motor, said lowering control circuit being unaffected by the interruption of the hoisting control circuit.

3. A hoist having a reversible electric motor, a motor hoisting circuit for operating said motor, a motor lowering circuit for operating said motor, a hoisting control circuit for one of the motor circuits, a lowering control circuit for the other motor circuit, a separate manually-controlled device for causing each of said control circuits to be energized and de-energized, and an emergency thermal cutout device associated with one of the hoisting circuits and actuated only by an emergency' temperature rise in the motor during its hoisting operation, said cutout device being operable independently of the motor lowering circuit and its associated lowering control circuit, and

being responsive to said emergency temperature to open the associated hoisting circuit prior to stalling the motor, said lowering circuits being unaffected by the interruption of the hoisting circuits.

CHARLES J. MANNE'YV HARRY D. MO ORE. 

